Genetic dissection of tropodithietic acid biosynthesis by marine roseobacters
Genetic dissection of tropodithietic acid biosynthesis by marine roseobacters
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DOI：
10.1128/aem.02339-07
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发表时间：
2008-03-01
影响因子：
4.4
通讯作者：
Belas, Robert
中科院分区：
文献类型：
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作者：
Geng, Haifeng;Bruhn, Jesper Bartholin;Belas, Robert
硅酸菌玫瑰杆菌菌株TM1040与鞭毛藻Pfiesteria piscicida之间的共生关系涉及细菌对鞭毛藻产生的二甲基磺酰丙酸（DMSP）的趋化性，DMSP的去甲基化，并最终在宿主表面形成生物膜。生物膜的形成与抗生素和黄褐色色素的产生同时发生。在本报告中，我们证明了抗生素是一种含硫化合物，tropodithic酸（TDA）。利用随机转座子插入诱变技术，鉴定出12个基因对细菌合成TDA至关重要，其中任何一个基因的突变都会导致抗生素活性（TDA(-)）和色素生成的丧失。出乎意料的是，6个被称为tdaA-F的基因无法在注释的TM1040基因组上找到，而是位于先前未识别的质粒（约130 kb； pSTM3）上，该质粒表现出低频率的自发丢失。通过诱变在另一种产tda的玫瑰杆菌Phaeobacter sp.菌株27-4中鉴定出tdaA和tdaB的同源物，该菌株也具有两个大质粒（分别为约60 kb和约70 kb），并且通过DNA-DNA杂交在9种已知具有抗生素活性的玫瑰杆菌的88%中发现了tda基因。这些数据表明玫瑰杆菌可能使用一种包括质粒编码蛋白的TDA生物合成的共同途径。利用元基因组数据库和生物信息学方法，观察了关键TDA合成基因在生物地理分布上的差异。讨论了这些结果对玫瑰杆菌存活的影响以及TM1040与其鞭毛菌宿主之间的相互作用。
The symbiotic association between the roseobacter Silicibacter sp. strain TM1040 and the dinoflagellate Pfiesteria piscicida involves bacterial chemotaxis to dinoflagellate-produced dimethylsulfoniopropionate (DMSP), DMSP demethylation, and ultimately a biofilm on the surface of the host. Biofilm formation is coincident with the production of an antibiotic and a yellow-brown pigment. In this report, we demonstrate that the antibiotic is a sulfur-containing compound, tropodithietic acid (TDA). Using random transposon insertion mutagenesis, 12 genes were identified as critical for TDA biosynthesis by the bacteria, and mutation in any one of these results in a loss of antibiotic activity (Tda(-)) and pigment production. Unexpectedly, six of the genes, referred to as tdaA-F, could not be found on the annotated TM1040 genome and were instead located on a previously unidentified plasmid (ca. 130 kb; pSTM3) that exhibited a low frequency of spontaneous loss. Homologs of tdaA and tdaB from Silicibacter sp. strain TM1040 were identified by mutagenesis in another TDA-producing roseobacter, Phaeobacter sp. strain 27-4, which also possesses two large plasmids (ca. 60 and ca. 70 kb, respectively), and tda genes were found by DNA-DNA hybridization in 88% of a diverse collection of nine roseobacters with known antibiotic activity. These data suggest that roseobacters may use a common pathway for TDA biosynthesis that involves plasmid-encoded proteins. Using metagenomic library databases and a bioinformatics approach, differences in the biogeographical distribution between the critical TDA synthesis genes were observed. The implications of these results to roseobacter survival and the interaction between TM1040 and its dinoflagellate host are discussed.